1. Field of the Invention
The present disclosure relates to the field of drive systems for potentiometer adjustment mechanisms, particularly those used in effects pedals that are used in conjunction with musical instruments.
2. Background
Potentiometers are widely used in applications where smooth control of an electrical device is desired, such as in controlling the volume of an audio device. In some devices, a potentiometer is connected to a knob to allow direct rotational adjustment, but in other devices it needs to be able to respond to forces in other directions, such as a linear force. In such devices, linear motion can be translated into rotational motion via a rack-and-pinion or cable-winding mechanism.
Effects pedals are one such device that controls a potentiometer via motion of a pivoting pedal. These pedals are connected between a musical instrument, such as a guitar, and an amplifier. A user rocks a pedal up and down to vary the volume of the guitar through the amplifier and achieve many interesting sound effects. Currently, these pedals use either a rack-and-pinion mechanism or a string to mechanically link the pedal to the potentiometer. Although commonly used in effects pedals, these mechanisms present several drawbacks.
In rack-and-pinion systems, the mechanism requires maintenance, such as lubrication and cleaning, to keep it running smoothly and avoid excessive wear. However, even sufficient maintenance cannot prevent gear lash, or slop, in the drive train to the potentiometer shaft. Further, a rack-and-pinion system can damage a potentiometer. A side load on the rack gear is required to maintain sufficient contact with the pinion gear, which can put a stress on the potentiometer shaft and shorten its life. In addition, a rack-and-pinion drive can skip a tooth and misalign the pedal position and damage the potentiometer. Finally, rack-and-pinion systems can create excessive noise, which could interfere with playing music.
String-drive systems eliminate some of the problems found in rack-and-pinion systems, but also have their own problems. String-drive systems can overlap their windings during use, which can cause excessive string wear, fraying, and eventual failure. When the string or cable breaks, it is difficult to repair. Further, string-drive systems can have tensioning errors during the full travel of the pedal, which requires springs in the drive train.
What is needed is a drive mechanism that can smoothly and quietly adjust a potentiometer, while operating with low friction, low wear, and high reliability.